CODEWITHSUNDEEP
c++randomprobability
Shehryar Farooq
Shehryar Farooq

Reputation: 115

Generate "characters" based on a probability

I need a little help with my tetris game that I am coding in C++ , here is my problem:

The list of tetris blocks are 7 types: {'I', 'J', 'L', 'S', 'Z', 'O', 'T'}

and i need to pick ONE of the above character such that S and Z are selected with probability 1/12 each, and the other blocks are selected with probability 1/6 each.

What is my best way to generate the blocks according to these probabilities?

Upvotes: 2

Views: 683

Answers (4)

Brian Driscoll
Brian Driscoll

Reputation: 19635

The easiest solution I can think of is to use numeric ranges and pseudo-random numbers.

So, first assign ranges to each letter:

I: 0 to 1
J: 1 to 2
L: 2 to 3
S: 3 to 3.5
Z: 3.5 to 4
O: 4 to 5
T: 5 to 6

then generate pseudo-random numbers within the range 0 to 6. Whichever part of the range that the number falls within, that's the letter you choose.

Unfortunately I do not know C++ so I cannot provide you with code, but I don't think it should be too difficult to implement.

Upvotes: 0

znarf
znarf

Reputation: 814

put those characters in a character array and generate random values from 0 to 6 with srand() than you can get a random

char myArray[] = {'I', 'J', 'L', 'S', 'Z', 'O', 'T'};

and then get values with

myArray[ (rand()%5)+1 ]

Upvotes: 1

Björn Pollex
Björn Pollex

Reputation: 76848

Create an array like so:

const char* block_distribution = {'I', 'I', 'J', 'J', 'L', 'L', 'S', 
                                  'Z', 'O', 'O', 'T', 'T'};

Then pick one element from that array using a uniform distribution.

Upvotes: 4

Pontus Gagge
Pontus Gagge

Reputation: 17268

Declare and define a twelve-item array with a single occurrence of S and Z; two occurrences each of the rest; and pick a random element from that.

Upvotes: 7

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